Wet clutches are well-known and used products. Wet clutches are utilized in many applications, including by way of example, wet-plate transmissions for off-highway vehicles and axle brakes. Typically, wet clutches are used to engage a portion of a driveline with a vehicle output or portions of a transmission to engage a specific gear ratio.
Friction separator discs, or plates, are a critical part of wet clutch shifting. During wet clutch shifting, the friction plates gradually degrade as their friction layer is worn off from physical and chemical processes. When the friction plates degrade, a torque transmission capability and a reaction of the wet clutch can be significantly reduced.
Currently, a remaining useful life of a clutch may be calculated in a static manner based on a number of shifts performed and/or a total time the clutch is used. As a result, the friction plates may be changed either too early, which results in unnecessary servicing of the wet clutch, or too late, which results in damage to the wet clutch.
At least one system is commercially available that is used for monitoring and prognostics of automatic transmission fluids for on-highway vehicles, known as Allison prognostics, supplied by Allison Transmission, Inc. While the details of the operation of Allison prognostics are not fully known, such a system does not appear to provide any information on a mean coefficient of friction for a clutch monitored by the system.
Therefore, the development of a monitoring and prognostics system for the friction plates is of paramount importance to achieve an optimal maintenance strategy for vehicles equipped with shifting wet clutch systems.
It would be advantageous to develop a monitoring and prognostics system used with a wet clutch system having friction plates that implements an optimal maintenance strategy based on information available from existing sensors used with the wet clutch system.